Radio receiving instrument for systems of broadcast distribution



Dec 11, 1928 E. E. CLEMENT OF BROADCAST DISTRIBUTION RADIO RECEIVING INSTRUMENT FOR SYSTEMS Filed Nov. 25, 1925 Patented Dec. 11, 1928 UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB TC EDWARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

RADIO RECEIVING INSTRUMENT FOR SYSTEMS OF BROADCAST DISTRIBUTION. v

' Application filed November 2 5, 1925. Serial No. 71,454.

My invention relates to subscribers station circuits and apparatus for combined telephone: and radio telephone systems, in

which current is supplied to the radio tel- 5 ephones as well as the telephones over a comapplication is a continuation in part of my copending application, Serial No. 720,870, filed June 18, 1924, and is also in the nature of an improvement over the invention described and claimed in my prior copending applications Serial No. 581,829, filed Au ust 14, 1922, Patent No. 1,522,357, patented anuary 6, 1925, and Serial No. 699,023, filed March 13, 1924. \Vhere the usual centralized battery is employed in a telephone system, a

29 constant potential is maintained on the lines,

and when the telephones are not in use, the radio telephones can be adjusted so as to function properly on the telephone current,

' using the metallic circuit only, without substation grounds; but it is desirable to compensate for the change in potential when a telephone transmitter of low resistance is bridged across the line, especially with respect to the filament current taken over that line. As disclosed in one of the applications referred to, a cut off relay is provided at the subscribers station, which becomes energized when the telephone is in use, to disconnect the normal charging circuit from the line to the radio telephone storage battery. In another application a bridged arrangement of both instruments is resorted to, the plate and filament circuits being parallel, with resistance interposed in the filament circuit. In the present case I employ a combination of the principles thus disclosed, using bridging circuits without grounds, and both compensating resistance and a booster battery which will automatically regulate the volts age and the current in the filament circuit when the telephone is in use.

A secondary object of the invention is to combine the circuits of the telephone and radio telephone at a subscribers station so that the radio messages may be received on the ordinary telephone receiver or on a special receiver attached to the telephone set, the combined instrument thus becoming an extension telephone with radio receiving attachment. 1

A third object of the invention is to provide means whereby the telephone hook switch may be disabled or mechanically locked while the telephone receiver is bein used for radio receiving, and therefore 0 the hook.

Other objects will sufiiciently appear from the detailed description hereinafter.

My invention is illustrated in the accompanying drawings, in which Fig. 1 is a diagram showing a, sub'scribers station provided with a floating booster battery, and a cut off relay energized when the telephone goes into service. to disconnect the adio telephone and its battery from the .Fig. 2 shows a similar arrangement of a booster battery, but with the cut off contacts of the radio telephone operated by the telephone switchhook. i

Fig. 3 shows a similar arrangement of a booster battery permanently connected to the telephone line terminals through choke coils to prevent leakage of telephone currents through the booster battery, as well as to regulate the flow of current from the booster into the telephone circuit.

Fig. 4 shows in skeleton outline the method of connecting a common booster bat f tery to a number of lines.

Fig. 5 is a diagram similar to Fig.1, showlng an electrical connect-ion from the radio te ephone set to the telephone receiver of the ordinar telephone set, together with means for mec anically locking and unlocking the switchhook of said telephone instrument, whereby its receiver may be removable for use as a radio telephone receiver, without closing the telephone circuits.

Fig. 6 is a fragmentary view of the upper portion of the desk standard equipped with a lockas shown in Fig. 5.

Referring to Figs. 1, 2, and 3 of the drawings, 1 and 2 are line wires leading from a telephone central ofiice to the telephone subscribers station T. At the central office end of the line suitable terminals are supposed to be provided, and abridged source of current such as the usual battery feeding into the line through typical choke coils. The usual voltage in manual telephone exchanges is 22. The usual voltage in automatic tele phone exchanges is 50, where electromagnetic switching is relied upon, and in the present case all the circuits shown and described have been tested on voltages ranging' "from 22 to 50, with entire success. Unless otherwise stated, however, in this application the central oliice battery may be assumed to deliver from 22 to 25 volts at its terminal. It need scarcely be said. that the choke coils at the central oilice are individual to the lines whenever the battery busses are connected thereto, these coils representing either cord circuit relay or repeating coil or choke coil units, or line relay windings normally included when the line is not in telephone use. Under all conditions, a steady how of current not exceeding 350 milliampercs may be assumed as within good practice, over the ordinary telephone lines, including paper cables. A larger current than this can be drawn through ordinary lines up to say one half ampere, without violating the underwriters requirements, but in such case special provision must be made for preventing operation of the ordinary sneakcurrent or heat coil arrestcrs, which are usually set at not to exceed 350 milliamperes for a limited time. The tube V employed in the radio telephone set shown is supposed to take onl milliamperes in its filament circuit, an a negligible amount in its plate circuit. As a matter of fact,'when the tests were made on these circuits, the best results were attained with a filament current not exceeding 50 milliamperes.

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Bridged across the wires 1-2 is the telephone T, having a transmitter 15, a receiver a, switchhook It, a ringer r and a 2mf con" denser C.

3-4. Wire 3 goes to the head set r from which wire 5 extends to the tickler coil 6 and thence to the plate p of the detector tube V. It should be stated that wire 1 goes to the positive or plus side of the central battery and wire 2 to the minus or negative side; hence the connection of the plate p of the subscribers vacuum tube is correct, being to the positive side of battery. Wire 3 is also connected to wire 5 through a compensating resistance Hz) to the filament rheostat of the tube V. The filament f is connect-ed on its other side to the wire 4 and thencebaclr through wire t to the No. 2 or negative side of line.

Units input side, the tube V has its circuit connected as usual through a grid condenser and a grid leak to the secondary coil 2' of the coupler coil I connected to the antenna circuit .{"--8. C is the tuning condenser lorthe antenna circuit, and C the corresponding condenser for the input circuit,

The operation of this circuit of Fig. l is Extending from the telephone terminals to the radio telephone set are Wires wearer as follows: through an ordinary line of ap potential available at the telephone terminals is from 18 to 20 volts, which is suilicient for the radio telephone circuits, both. plate and filament, using a detector and tele phone head set only. With the telephone in the position of disuse as shown in the draw ing, the full voltage and full current supplied over the line are available for the radio telephone. It the telephone receiver 1 is taken down for use, however, during use of the radio telephone, it will be observed that a direct bridge of low resistance is put across the line by way of the wire 1, windin i of the induction coil 1, switchhook h, and telephone transmitter t. This draws enough current from the line to cause a decided drop in potential, which must be compensated for, especially in the filament circuit of tie dio telcp 10118.. This compensation is ciiected through the use of booster battery B.

The circuits shown in Figures 1, f2 and 3 are only three out of a large number that might be presented in which a booster battery is the main feature. In the present case this battery maintains the voltage on both the plate and filament circuits of the radio telephone, and is normally charged from central at all times when the telephone is not in use. Also, it is possible to place a booster battery at a central point, putting it in the line, in series with the ordinary battery supply, so that for example when a line is in use for radio receiving it will have imposed upon it a total of say 50 volts, onehalf of which is derived from the bridged main telephone battery, and the other half from the series booster battery included in the individual line. This booster battery may feed more than. one line, being provided in such case with bus bars accessible to all the lines requiring boosting and one side of each line may be opened and the ends connected to opposite bus bars of this booster battery, through choke coils as shown in Fig. l. in such case the continuity of each line may be preserved by bridging the gap thus produced by a talking and ringing condenser of say 2mf capacity. has hereinbelorc stated, the choke coils on op posite sides of these condensers, must be individual to the lines in order to prevent cross-talk through the booster battery buTsses. (See Fig, 4;.)

Referring to the specific bridge booster batteries herein shown, especially the arrangement of 1, went off relay R has its windings included in series with the telephone transmitter t and shunted by a condenser C so thatwhen the telephone is in use, relay it is energized to pull in its armatures and disconnect the wires 3- l from the line wires l-2. Across these wires 34: between the radio telephone and the 7 wires 3 and 4, are connected the circuit.

telephone is bridged the booster battery B, consisting of the same or approximately the same number or cells, and having the-same normal voltage, as the main telephone battcry at central, and connected with the same pole and the same sides of line. Normally this battery is charged from the central oiiice. and when the cut oil relay R is energized, battery 13 carries the load until the telephone again goes out of use.

In Fig. 2 the same arrangement of booster battery is shown with the same radio telephone circuits and the same telephone circuits, but instead of a cut off relay, the and disconnected to and from the line wires 12 by means of switchin terminals it, if, h, h, controlled by he switchhook It and when the hook is up these are open, when it is down are closed. When the hook is up the ra io telephone and booster battery are therefore cut off from the telephone line, and when the hook is down they are connected thereto.

Fig. 3 shows a modification employing the same radio circuits and battery and the same telephone, but without any cut oil". In thiscase the battery is permanently connected across the line, through choke coils 6 similar to the usual choke coils at the central ofiice. In this case when the telephone is in use, it draws a certain amount of current from the booster battery, in parallel with the main battery, 2. pair of substantially identical choke coils. The booster battery however, owing to the line resistance will furnish somewhat more than one-half of the current absorbed in the telephone circuit, unless the resistance of the coils b or other compensating resistance is adjusted to balance. Various arrangements for this urpose will suggest themselves to those amiliar with the art. The main point is that in this case the battery is permanent-l floated on the line, and

. its'charge and discharge currents ebb and how according to the conditions on said line.

In Fig. 3, there can be no leakage between telephone and radio telephone, since the choke coils b prevent the passage of voice current into the radio telephone currents, and the bridged battery, having a very low internal resistance, short circuits all audio currents originating in the radio telephone This is desirable where the two pieces of apparatus are permanently con nected to line, although as stated before, subscribers sometimes actually prefer to hear the radio broadcasting in their telephone receiver, and if there is leakage, this also affords an opportunity for the central oilice operator to listen over the line.

Fig. 5 shows the same diagram as Fig. 1, with the exception that the secondary z" of a radio receiver induction coil. is connected each feeding through through switch S with windings of the ordinary telcphone receiver 1" forming a part of the telephone set T. In order that the receiver 7* may be used to listen to radio communications without closing the telephone circuit, I provide a mechanical lock consisting of a ring or collar L (see Fig. 6) at the head of the column of the desk stand, with a notch in it normally lying over the lever of the switchhook h. In this position, the telephone receiver may be taken down for ordinary telephonic use, and an index marked Z on the collar then registers with a corresponding index marked 3*, onthe desk stand, marked tel The collar L has a handle and by means of this the collar can be rotated until the index marked 1 registers with a second angular displaced index mark Z rad. In this position of the collar L, the notch Z will have passed beyond the shank of the hook it so that the latter cannot rise but is locked. Hence the receiver can be safely removed therefrom without closing the telephone circuits. The switch S may be operated manually or otherwise so as to close the radio circuit and the telephone receiver when the telephone switchhook is locked and not otherwise. As a matter of fact, I have found by actual test that persons using the telephone are not seriously disturbed by receiving the radio modulations in the same receiver, unless the latter are amplified so as The switch S may cut in a regular headset when the telephone is in use, if desired, but in practice it is thought this switch will be best regulated by the subscriber himself.

What I claim is: 1. In av combined telephone system and radio telephone system, a pair of line wires,

a central office source of current supply for said line Wires, a subscribers telephone of relatively low said line wires, asubscribers radio telephone of relatively high resistance also connected across said line wires, means for supplying current from said central source ata fixed voltage to either or both of said instruments over the line wires and a booster source of current arranged to supply extra energy to the radio instrument to compensate for the drop in voltage when the telephone instrument is put in use simultaneously therewith.

2. In a combined telephone system and radio telephone system, a central oflice source of current supply for said line wires, a subscribers telephone of relatively low resistance connected across said line wires, a subscribefs radio -telephone of relatively high resistance also con nected across said line wires, means for supplying current from said central sourceat a fixed voltage to either or both of said instruments over the line wires, and a booster battery normally bridged across the radio to be very loud. I

resistance connected across a pair of line wires,

4. The system claimed in'claim 2 with a; relay energized in series with the telephone circuit and operable upon energization to open the line circuit between the radio telephone and the telephone, leaving the booster battery connected to the radio telephone terminals.

5. The system claimed in claim 2 with a switch controlling the telephone circuit and provided with contacts arranged to open the ine circuit between the radio telephone and the telephone upon raising of the switchbook of the latter.

In testimony whereof I'hereunto aiiix my signature.

EDWARD E. ELEMENT. 

